Keyframes are added to video streams to begin a stream, to change key properties (like resolution), to resynchronize after loss, or to allow additional receivers to start consuming the stream. Keyframes are free of dependency on other frames in the video sequence, and in doing so, are restricted to a subset of compression techniques, which cannot achieve the same degree of compression efficiency as inter-frame dependency. In low-latency channels with constrained bandwidth, the size of a keyframe is to be kept comparable with the typical frame, or it cannot be delivered without delay. This leads to low-quality keyframes that are degraded in quality relative to typical frames. In low-latency bi-directional video communication, keyframes are usually sent when requested by an existing or new recipient.
The requestor of the keyframe is often not as sensitive to this loss of quality as others who are consuming the stream. When the Nth participant starts to consume a stream shared with others, that participant starts from nothing and is little affected by the low quality of the first frame. But the N−1 participants already viewing the stream will see a short-term loss of quality, caused by the keyframe. Similarly, a participant who has experienced packet loss, will see a broken stream (if not concealed by freezing) repaired by an eventual keyframe that is requested. Other participants will experience a temporary degradation, with no gain.